Optical and Near‐Infrared Model Images of the Circumstellar Environments of Classical T Tauri Stars

Abstract

We describe model calculations of optical and near-infrared scattered light images expected from class II T Tauri starsEthe star-plus-disk systems. The parameters controlling the disk shape, size, and mass are chosen to be within theoretically and observationally derived limits. We restrict our models to nearly edge-on disks, since for lower inclinations the central starlight is many orders of magnitude greater than the radiation scattered in the disk. In addition to model Nux images, we calculate spectral energy dis- tributions for pole-on viewing using approximations for Nat and Nared disks. We -nd that direct imaging of edge-on disks can provide only estimates of the scale height at large distances from the central star and an estimate of the disk mass. The images are rather insensitive to the inner disk radius and the degree of Naring, provided the scale height is -xed at large radii. Spectral energy distribution modeling is required to constrain the inner disk radius and the degree of Naring. We apply our models to recent Hubble Space Telescope (HST ) images of HH 30 IRS and investigate whether the scattered light images could have been produced by starlight scattering o† the walls of jet- carved cavities in infalling envelopes associated with the embedded class I sources. We -nd that while the class I infalling envelope plus cavity model qualitatively resembles the HST images, the spatial extent of the model images is too large. Edge-on disk models appear to provide better -ts to the data and enable us to determine the disk scale height at large distances from the central star. However, the assumption of axisymmetry and uniform illumination is clearly inadequate for this variable source. In addition to producing Nux images, our radiation-transfer simulations predict the spatially resolved polar- ization structure of HH 30. We have also performed K-band simulations for HH 30 in anticipation of high-resolution infrared imaging polarimetry. Subject headings: circumstellar matter E radiative transfer E stars: individual (HH 30) E stars: preEmain-sequence